General Formation of Monodisperse IrM (M = Ni, Co, Fe) Bimetallic Nanoclusters as Bifunctional Electrocatalysts for Acidic Overall Water Splitting

The development of bifunctional electrocatalysts for overall water splitting in acidic media is vital for polymer electrolyte membrane (PEM) electrolyzers, but still full of obstacles. Here, highly efficient acidic overall water splitting is realized by utilizing ultrasmall, monodispersed Iridium (Ir)‐based nanoclusters (NCs) as the candidate, via a surfactant‐free, wet‐chemical, and large‐scalable strategy. Benefiting from the high specific surface area, clean surface, and strong binding between NCs and supports, the IrM NCs exhibit attractive activities and durability for both oxygen evolution reaction and hydrogen evolution reaction in acidic electrolytes, with IrNi NCs showing the best performance. More significantly, in the overall water splitting, IrNi NCs reach 10 mA cm −2 at a cell voltage of only 1.58 V in 0.5 m H 2 SO 4 electrolyte, holding promises for potential implementation of PEM water electrolysis. This work opens a new avenue toward designing bifunctional “acidic stable” catalysts for efficient overall water splitting.